diff -r 0b5b757ca812 -r 9fa5b8f4e98e src/topic/__init__.py
--- a/src/topic/__init__.py	Wed Jun 10 16:20:05 2015 -0500
+++ b/src/topic/__init__.py	Wed Jun 10 16:23:56 2015 -0500
@@ -64,7 +64,7 @@
             'topics', 'topic', namemap=_namemap, nodemap=_nodemap))
     repo.__class__ = topicrepo
 
-@command('topics', [
+@command('topics [TOPIC]', [
     ('', 'clear', False, 'clear active topic if any'),
     ('', 'change', '', 'revset of existing revisions to change topic'),
 ])